Prismatic directional and object locating system

ABSTRACT

696,809. Acoustic directional apparatus. WESTERN ELECTRIC CO., Inc. Sept. 3, 1943 [March 12, 1942]. No. 14457/43. Class 118 (ii) [Also in Group XL(c)] A system for detecting or locating an object .such as a submerged submarine by the reception of compressional waves originating at or reflected from the object, or for detecting or locating an object such as an aircraft in flight by the reception of electro-magnetic waves reflected from the object (see Group XL(c)) includes a device directionally responsive in different directions to different frequencies and means to determine the frequency of the wave and hence its direction. When compressional waves are used both the transmitter (when used) and the receiver are &#34;frequency directional&#34; and the same apparatus may function as transmitter and receiver alternately; when electromagnetic waves are used either the transmitter or the receiver may be &#34; frequency-directional.&#34; For compressional wave work the transmitter / receiver may be generally as described in Specification 592,255 which comprises a multiplicity of rows of piezoelectric crystals, the rows being separated from one another by a distance less than half of the minimum wave length to be used and successive rows are shunted across successive shunt arms of a multi-section electrical wave filter which passes the range of frequencies of interest. Such transmitter acts like a prism and spreads the range of frequencies like a spectrum and directs each particular frequency in a distinct direction; similarly the receiver may receive any given frequency from one direction only. Fig. 1 shows three transmitter/receivers 17, 19, 20, of which one is positioned in each side of a vessel and the third beneath the vessel, Figs. 3A and 3B (not shown). The output of one of the receivers is connected by a switch 18 to a filter 149, which excludes extraneous interfering frequencies, and a modulator 26 where it is combined with the output of a variable heterodyne &#39;oscillator 28 furnishing a heterodyne frequency varied periodically over a range of say 118/124 Kcs. so that any frequency received within the 18/24 Kc. range normally used in subaqueous transmission will produce a beatnote of 100 kcs. which is passed through a filter 32 and rectifier 34 to the control anode 38 of a cathode ray tube 85. The beam is deflected horizontally by a variable voltage from battery 22 through potentiometer 30 which voltage varies periodically with the frequency changes of oscillator 28. A scale 81 against the screen 36 gives the horizontal angle of reception. The receiver 20 beneath the vessel is rotatably mounted and a variable voltage is applied to the vertical deflecting plates of the cathode ray tube from a battery 43 and potentiometer 44 syncronously with the turning movement of receiver 20 so that the vertical angle of reception may be read on a scale 83. A second cathode ray tube may be provided to give a direct reading of distance Fig. 2 (not shown). In Fig. 4 several buoy systems may be installed in narrow channels, harbours etc.; each buoy supports two receivers of which one, 74 is directive in a horizontal plane the other, 72, in a vertical plane. Noise from the propeller of a submarine 70 picked up by one of more of the receivers is converted into low frequency current which is used to modulate carrier radio waves of distinctive frequencies emitted by small radio transmitters 82 and picked up by an attendant vessel 88. A transmitter/ receiver having frequency-directivity in both horizontal and vertical planes may be used, Fig. 5 (not shown).

Nov. 3, 1953 w, MASON 2,658,186

PRISMATIC DIRECTIONAL AND OBJECT LOCATING SYSTEM Filed March 12, 1942 4 Sheets-Sheet l PRISMA T/C REC-RAD.

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PRISMATIC DIRECTIONAL AND OBJECT LOCATING SYSTEM Filed March 12, 1942 4 Sheets-Shet 4 SEND/N6 5 VS TE M /4 r/Lrsn r01? $52 25??? Fla 7 LIMITING FREQUENCY RANGE RECEIVING SETS FOR RECT/F /NG IND/CArl/VG FREQ. RJNGES SIGNALS PECE/l/ING 5V5 TEM Lg i5 nnmmuu m 39% 220 222 224 230 232 'wumumm Z $15 mmuuuuun 51 39%;)

INTO DEFIN/TE LENS FOR IL FREQUENCY RANGES FOCUS/N6 RANGE: 47' R0175 OI RECEIVING SETS ATmRNEV Patented Nov. 3, 1953 UNITED STAT YT; if;

OFFICE PRISMATIC DIREGTIONAL AND OBJECT LOCATING SYSTEM Application March 12, 1942, Serial No. 434,396

14 Claims.

This invention relates to directional systems, such as object-locating or detecting systems, navigation aiding systems and the like, employing prismatic wave energy transmitting or receiving devices. More particularly, it relates to systems for locating or detecting objects, obstacles, etc., by compressional or radio wave energy which may originate at or be reflected from the object to be detected, the systems employing prismatically directive transmitting or receiving devices to afford directional indications and thus eliminate in part or entirely the mechanical manipulation of directive devices to afford directional indications. A particular application to directive communication systems is also described.

Objects of the invention are to provide aids to navigation of mobile craft, to facilitate the detection and location of hostile craft and to provide systems for accomplishing these objects which require little or no mechanical scanning.

A particular object is to provide an improved method of detecting the direction from which noise vibrations impinge upon a receiving device.

Another object is to provide a unique directional communication system employing a prismatic directional device to direct communication channels to particular desired stations of a plurality of stations.

A further object is to provide submarine searching systems which will substantially eliminate tedious manipulation of searching equipment and will greatly increase the effectiveness of submarine scarching operations by increasing the ease and speed with which they can be effected.

An additional object is to provide submarine searching apparatus and systems which will be substantially free from interference caused by noise originating on the searching vessel itself so that the latter will not be hampered in its search by a necessity to slow down so that its own engines noises will not mask the noises of the craft being sought.

Further objects will become apparent during the following description of preferred illustrative embodiments of the invention and from the-appended claims.

This invention, in a major aspect, is directed toward the more practicable solution of the important and difiicult problem of locating enemy craft, particularly submerged submarines. Comradiating and receiving members which have .50 pressional wave radiating andreceiving apparabeen, in general, bulky and difiicult to manipulate. Prior art devices have, in general, not afforded as high a degree of directivity as is desirable, a particular difficulty, for example, being that propeller noise from the searching vessel itself interfered with and masked noises from the hunted craft. In addition to this, the necessity of mechanically pointing the directive radiating and receiving devices ledto many practical difiiculties and together with the limitations imposed by propeller noise made it necessary in many intances to bring the searching craft to a very slow speed and, frequently, pointing could be effected only by pointing the whole vessel. Also with many prior art systems it is not possible to detect a submarine passing beneath the searching vessel. These diiiiculties naturally greatly reduced the efiicicncy and expedition with which submerged vessels could be located and followed.

By devising systems employing prismatic radiating and receiving structure, the necessity of mechanically pointing a directive device can be largely obviated and the rapidity with which the desired areas may be scanned can be greatly increased. Furthermore, the majority of the de-.

vices employed in systems of the invention are stationary with respect to the vessel on which they are mounted and they can be streamlined. Since devices of the invention can largely eliminate interference from the propeller noises of their own craft, the latter can proceed at'any speed desired without interfering with the efficacy of the searching operation.

For a' submerged submarine in motion, the propeller noise is the usual telltale indication sought to be detected. Since noise comprises a very broad band of frequencies and a prismatic receiving device selects for each angle of approach thereto a particular frequency, it is merely necessary to note the frequency being received in order to obtain an indication of the angle at which the noise is approaching the receiving prism. If several frequencies are being received, it is an indication of several sources of noise at different directions, the respective directions being indicated by the respective values of the received frequencies. A frequency analyzer and an indicating device which will, in eifect, plot each received frequency on a base scale representing the angle of approach "will then suffice to indicate the presence of and direction to noise sources within the range of the receiving system.

For harbors, coastal waterways and narrow channels, it is practicable to submerge prismatic receiving devices at suitable intervals, preferably I anchored and i associated I the surface carrying small radio, transmittin I I which is modulated by I i 1 low frequencies corresponding with those of the q buoy transmitters, the position and course moving submarine relative thereto can be readily scribed hereinafter;

I 1 energy impinges.

I vice can then e g I I received; by :it will each indicate a reflecting obsets; the radio. carrier 7 of sound received by the prismatic receiving device. By noting the modulations of of a with buoys floating on several successive 7 Fig; 5 illustrates an arrangement providing 7 compound prismatic properties .to provide the distribution of afrequency spectrum over an area or the equivalent of p'ointby point scanning of y an area without mechanical manipulation of the directing devices;

Fig. 6 is'a further system'of the invention em- .ploying compound prismatic radiation of elecooserved on surface craft, such as submarine 'chasers, and steps can thenbe taken to intercept" and destroy the submarine- I I I solutions for which. are de i A iurtherproblem,

that of detecting the presence and location of inert objects such as sub-- ,marineslying in wait with still engines; Since such objects radiate no; compressional wave or other'readily detectableenergy,itismostfeasible i Q veyed and to receivereflections of such :stantial'vslue in'such systems.: The energy-em the pass b'and of the prismatic devicejemployed.

be. employed and the frecpiencies the band of noise fr'el to project energy over the areaor region to be sur- I I 7 energy from objects suchfas: submarines upon which the;

Systems employing prismatic I I both are also of 's'iibs area.

, 1 loyed can again :very conveniently be noise, j I "comprising substantially all frequencies within will indicate the directionof the reflecting object from the-transmitter, jor' e I quencies can be radiated to entirely cover; the

area to be'explored' and'aprismaticreceiving de-t s 1 ject at a particular angle with respect to there-, I

ceiver. the receipt of the several reflections may be timed to provide distance as well as directional indications with respect to reflecting objects;

Several types of indicating devices and arrangements for the various forms of directive systems of the invention are also. shown and described hereinafter as well as the application of the principles of the invention to directive transmission of'intelligence for communication or for the navigation of mobile craft.

The arrangements and principles of the invention will be more readily understood in connection with the detailed description of illustrative embodiments given below in conjunction with the accompanying drawings, in which:'

Fig. 1 illustrates. in block diagrammatic form a system of the invention in which a plurality of compressional wave prismatic receivers are employed, in conjunction with a frequency analyzing circuit and an indicator to provide indications of the presence and direction of noise sources;

Fig. 2 illustrates in block diagrammatic form a system of the invention for transmitting compressional wave noise energy and receiving refiections thereof to provide indications of the presence and direction of reflecting objects;

Figs. 3A and 3B illustrate an arrangement of prismatic devices on a marine craft suitable for use in systems of the-types of Figs. 1 and 2 for submarine detection and object location;

'Fig. 4 illustrates the use of prismatic receivers submerged and associated with buoy type" radio transmitters forthe detection and location of submarines, in harbors, channels and the like;

Pulses of noise can be'transmitted'an'd' 7 terest.

T In more detail in 1g.

'ception for object location.

Fig. "I is a further'system of the invention em- I -pl'oying; nOn directional transmission and *COIIl-r pound prismatic reception of electromagnetic I I I g waves for objectlocation; and

g'ational system.

Receiver-radiators ll, 19 and 2B are prefershunt. arms are multisection electrical wave filter which'passes the range of frequencies of in- Such devices are characterized by prismatic directive properties which are a function of frequency within the frequency range of interest and spread the range as a spectrum if transmitting it, or selectively receive frequencies within the range of interest only if they impinge upon the receiver at a particular predetermined angle for each particular frequency.

For purposes of illustration it is assumed that these receiver-radiators pass the frequency band between 18 and 24' kilccycles which is commonly employed in submarine signaling systems.

As described in my above-mentioned copending application, such a receiver can readily be constructed to cover ahorizontal range as great as degrees desired and a vertical range of approximately 10 degrees which will suffice to detect noises from submarines at normal depths and at reasonable distances from a surface craft. In order to be able to detect and follow submarines "close to the surface vessel, or passing under it,

it is desirable to be able to cover the area beneath i the ship also and the mechanical arrangement of the special'mounting of prism 20' on a rotatable shaft 58 for this purpose is also shown in Figs. 3A and 3B.

In Fig. 1 the output of one of the receiverradiators- I1, is or 20- is selected by switch l8 and introduced through filter I49 which passes frequencies within the band of interest but excludes extraneous interfering frequencies, into modulator 26 where it is combined with the output of variable heterodyne oscillator 28 which furnishes a heterodyne frequency varied periodically over the range of- 118 to 124 kilocycles, so

Fig. 8 i a system of the invention applyin prismatic transmission'and broadly directional reception for a selective communication or: navi p I, one of thethree com pressional wave prismatic receiver-radiators11, f'

is selected by switch 18 to: receive com- ,pressional wave energy from a predetermined For examplathey maybe mounted su merged on the sides and heel of. the prow of a marine craft as illustrated in ifigsLEA and, 3B so t'hat all compressional wave vibrationsinthe waterapproachingfrom the sides of the craft or 1 from. beneath the craftwill strike the, receiving i i ,surfaceof one of the prisms ably of the multic'rystal ,Rochelle'salt piezoelec tric type described in: detail in-my' appending api I Z plication, Serial'No. 431,558, filed February '19, 194-2, relating to fPrismatic compressional Wave Radiators and Receivers}? now United States Pat 1 ent2,4f0,391-,1granted July 23., 1946, comprising 1 'a plurality of rows; of piezoelectric crystals, sucq 'cessive I rowsbeing shunted across successive Z that any frequency within the rang of 18 to 24 kilocycles, as received by receiver-radiator l1, H! or 20 will produce a side-band frequency or beatnote of 100 kilocycles at some point in the frequency range of the heterodyne oscillator, and the l-kilocycle side-band will pass through filter 32. The frequency variation can be continuous under the drive of motor 3| from battery 31, switch 35 being closed, or it can be manually controlled by handwheel 33, with switch 35 open, so that particular reflections can be examined closely.

The output of filter 32 is rectified by rectifier 34 and employed to operate an indicator, in this instance a cathode ray tube 85 having a target 36 and a control anode 38 which latter is employed in the present instance to substantially increase the intensity of the cathode ray beam upon the receipt of a signal in accordance with the rectified output of device 34.

The beam of the cathode ray tube is deflected horizontally by a variable voltage obtained through potentiometer 36 from battery 22- which voltage is varied periodically with the frequency changes of heterodyne oscillator 28 as indicated.

The successive horizontal positions of the beam of the cathode ray oscilloscope will, therefore, correspond with successive frequencies in the range of 18 to 24 kilocycles which, in turn, correspond with successive directions of reception of the prismatic receiver-radiator l8, H! or 29 as selected by switch l8. A scale 8| associated with target 36 enables the observer to read the horizontal angle of reception corresponding to each signal received.

If it is desired to sweep a greater vertical angle than degrees, as for scanning the area beneath a searching craft, the receiver-radiator 20 can be rotated or oscillated on a shaft 58 through any desired vertical angle and a second potentiometer 44 can provide a variable voltage to vertical deflecting plates 42 from a battery 43 to deflect the beam of cathode ray oscilloscope 36 vertically in synchronism with the turning motion of the receiver-radiator 20, whereby a pattern of indications, showing the horizontal and vertical angular directions of submarines or other noise sources within the area scanned, will be obtained. A vertical scale 83 is also associated with target 36 to enable the observer to read the vertical angle corresponding to each signal received.

As indicated in Fig. 3A, the shaft 58 carrying receiver-radiator 20 is preferably power-actuated as by a motor 56 driven from battery 64, with switch 4| placed in its upper position to make direct connection to the battery, the motor 56 being arranged in a manner well known in the art to reverse its direction of rotation after turning through the desired arc. Alternate manual remote control is provided by a selsyn or similar well-known remote control arrangement including unit 63 which can be connected to the driving motor 56 by throwing switch 4! to the position shown in Fig. 1. Unit 63 is then turned by handwheel 65 and motor 56 duplicates the movements imparted to unit 63, to permit detailed observation of signals of particular interest without sweeping through the entire arc normally covered.

The system of Fig. 2 differs from that of Figenergy to actuate the transmitter.

provides for alternately connecting the transmitter 46 and the modulator 26 to the prismatic receiver-radiator l1, l9 or 20 as selected by switch l8. Transmitter oscillator 46 obviously need operate only during transmitting intervals. Modulator 45 can conveniently, therefore, furnish relatively short pulses of resistance noise The duplexing circuit 48 may be of the type well known in the art, which short-circuits the receiving modulator 26 input when the transmitter operates and opens it when transmission ceases. The impedance of transmitter 46 should be high when it is not operating so that it will not appreciably decrease the received signals reaching modulator 26. Distance to objects of particular interest may readily be ascertained by determining the reflection time of regularly emitted pulses using any of the several well-known pulsereflection circuits of the art. In accordance with one well-known system, when a signal of particular interest has been selected switch 10 is thrown to its lower position to place the output of rectifier 34 on the vertical deflecting plates 42 of a second cathode ray oscilloscope 81. The horizontal deflecting plates 40 of this oscilloscope are connected to a sweep circuit 69 which is synchronized with the outgoing pulses to deflect the ray uniformly with time, as indicated by trace 61, across the target 66. The received reflection produces a vertical deflection such as 68 the lateral position of which indicates the distance to the reflecting object, which may be read from scale 89.

With oscillator 46 deenergized, the system of Fig. 2 may of course be used for detecting noise sources in the same manner as for the system of Fig. 1. In the system of Fig. 2 receiver-radiators l1, l3 and 26, are of course, alternately used as receivers and as radiators as required for the operations it is desired to carry out.

In Figs 3A and 3B a suitable physical arrangement of the plurality of prismatic receiver-radiators I1, l9 and 20 on the hull of a power propelled marine craft is illustrated. Devices l1 and [9 are arranged on the port and starboard sides, respectively, of the prow of the craft and taken together will directively receive or transmit compressional wave energy of proper frequencies in view of their prismatic properties within avertical arc of approximately 10 degrees from the horizontal and from substantially any horizontal direction save for a small arc toward the rear of the vessel, which purposely includes the position of the propeller of the craft itself so that noises therefrom will not be efificiently received. These devices can offer substantially streamlined surfaces to the water in order to reduce the drag of the water upon them.

Prismatic receiver-radiator 20 is mounted in a streamlined nacelle 60 on the keel of the craft. It is rotatable at least through an arc of substantially degrees so that it may be employed to scan the areabeneath the craft for the purpose of detecting submarines or other objects rents.

Figs; 1 and. 2.- The system of Fig; 2- is naturally, I

preferable since it permits detection of inert ob:- jects as wellas of noise sources. a

In Fig. 42', two submarine detecting stations are shown and comprise prismatic compressional wave receiving devices-"12,714, T6 and; 18 which are suspended, submerged in water 10?, on cables 15' and 19', as shown respectively, the anchors I3 and IT holding the lower endsqcf the" cables in the bottom I02 and the buoys B0 and 84 supporting the upperv ends thereof, respectively. Devices l4" and J8 are'prismatically directivein the horizontal plane and devices; 12 and 15- a-re prisman "cally directive in the vertical plane; The

particular frequenciestreceived by these devices will;- of. course, dependupon the" respective angles at which the noise emitted by the. submarine 10 impinges upon them-and they will generate currents the frequenciesof which will correspond which emit carrier radio waves of, distinctive v frequencies, from antennas 82- and 86;, respectively. Cables 15 and 19 include conductors serving-r to connect devices 12, 14', 16' and 18 to" the transmitters intheir respective buoys to modulate the" carrier waves above mentioned, with their respective .low frequency output cur- Additional detecting stationsincluding buoys, cables,- prismatic r'eceivers,- anchors, transmitters and antennas, aslfor the two detecting stain'ons above described; are spaced at con- L veni'ent intervals about an area to be patrolled, for example; a-hazrbor orship channel. The-area can'th'enbe'p-atrolled by. carrying a radio receiving system, including antenna 96 on asurface craft 88. The radio receiving system can, in turn, 2

be tuned to the carrier waves emitted by the successive buoys. Upon" noting the low frequency modulations on each carrier an observer onthe patror craft can'deduce therefrom the position and Course of the submarine and can initiate, or direct, appropriate action to" capture or destroy it;

Obviously, the two prismatic receivers at each detecting station can be replaced by a single-compound compressional wave prismati-c receiver, the principles of which will become apparent in the discussion" of Fig; 5 to' be describedpresently.

Obviously,. also, similar arrangementsbf detec'ting stations can readily be devised for other purposes-than detecting submarines; Forenam- 'ple; prismatic receivers designed for use in' air can beplaced at advanced points in an air-raid defenses'ysteni and connected to modulate lowpower radio carrier waves which can be'received at convenientobservation points whereby time- 1y warnings of the direction of approachof hos tile aircraft'can be obtained. Such systemswi-ll in sbme measure assist in overcoming themain objection to sonic aircraft detecting systems"i.-:e.,

because of the time requiredfor the sound" of aircraft to preach the ground the craft have passed well beyond the observation point by the time the sounds have been, received and interpreted.

.In Fig.-5 the-essential elements of a compound prismatic (of doubly prismatic) receiving or radiating system-is shown. A first; or primary prismatic radiator or receiver H14; serves to impart directivity vertically to-severalgroupgotfrequencies'which together comprise theentire band to be employs of frequencies employed. Thereafter, horizontal directivity to the frequencies within each group is imparted by a-plu-ral-ity of secondary prismatic devices IBS to H2, inclusive. I i

Device H14 is preferably of the multicrystal, filter-coupled type described in detail in nependin'g application entitled Erismatic and-l-Iigh Power -Ccmpressional Wav e Radiators and Receivers, Serial No. 431,558, filed February 19, 19142; which matured into United States Patent 25404-391, granted July 23, 1946; in which a plurality of rows of piezoelectric crystal vibrators are coupled to successive sections of a multisection. electric wave filter, the phase per section of the filter varying between prescribed limits as the frequency is varied between the limits of the frequency range employedh h 1 In the system of Fig. 5 the energy emitted directivel-y from the prismatic device N14 is iocuse'd by cylindrical lens Hi6 on the inputs of a secondary series of prismaticdevices Hi8 to I l}, in elusive, the total frequency range employed being in" eff-ectsubdivided into five approximately equal parts and device 14' and lens Hi6 being proportioned so that these five equal parts" dis,- tributed' vertically in the order of their mean irequencies'to the inputs of the five secondary series of prismatic devices I N18 to Hi, respectively. Small portions of the frequency range will, of course, be partially or wholly ineffective because they are directed too close to the edges or their respective secondary prismatic dev'ie e'ser mm intervals between successive secondary prismatic devices. U

To effect this vertical distribution by parts, or the total frequency range employed, the prematic device it]; isprovided with acoupling filter the sections of which have ,a relatively smaller rate of change of phase with frequency over the range employed than where a more complete and distinct separationof the individual frequencies of the range employed is desired; One obvious method or obtaining" a smaller rate of change of phase with frequency is' to broaden the trans mission band of the coupling filter" so' that the limiting wrexuaneiowerand upper) frequencies passedare waibeyond the lower and upper frequencies, :espectively; of the frequency range I v 'd, This follows, of course, from thefact that an electrical wavefilter section has substantially the same total difference phase shift in passing from its lowert'o its upper cutoff frequencies vregardless of the width of it's band;

lf a singleprimary prismatic device such as i-Mis employed, itfla'gainlfollows that the" total verticalangular' distribution to be obtained over the frequency ran e employed mustbe'con'sidfably less than' 180' degrees since only a portion of the total phase shift per section-of the coupling filter is to be employed, as above eic'plaihed;

It a greater vertical angle of distribution is desired; two or more systems of the type illustrated-- in l*"ig S may, ofcourse, be employed and aligned so that their ranges are contiguous and together cover the-entire vertical angle desired.

The secondary prismatic devices 108/00 H2, inclusive, serve; as above mentioned; to impart horizontal directivity, i. e:, to spread horizontally, the several frequencies of the frequency bands directed to them, respectively, by the device Hi4 andlenslflt. flfhese secondary prismatic devices can conveniently be of similar design to the device of FigLHlZ of my copendi'ng applidatiohehtitled compressional Wave Directional; Prismatic and Focusing Systems, Serial No. 425,710. filed January 6, 1942, now United States Patent 2,406,391, granted August 27, 1946, except that, obviously, compressional wave energy is projected directly into them from prism I04 instead of being generated in them by piezoelectric vibrators as shown in Fig. 12 of my above-mentioned application. For the secondary prismatic devices also it will generally be desired to spread the frequency band through an are considerably less than 180 degrees so that only the central portion of the pass-band of the filter structure incorporated in the prismatic device will be employed and a smaller number of units per secondary device will sufiice than where a wider angular distribution and more highly directive properties are necessary.

From the above description it is apparent that the system of Fig. 5 results in spreading the frequencies of the range employed, vertically and horizontally so that the device may be employed to cover an area with compressional wave energy the energy being spread prismatically in the two directions so that within the area a different frequency will be found to impinge upon each unit of area.- The size of the unit of area in which a particular frequency will be encountered will of course be determined by the over-all characteristics of the compound prismatic device, as will become more apparent hereinafter.

Conversely, when employed as a receiving device in a detecting system, such as that of Fig. 4, for example, the position of a source of noise within the area can be determined simply by determining the frequency of the component which is received by the system of Fig. 5.

As an alternative to employing the prismatic device I04 together with a lens I06, the prismatic device I04 can be constructed with its emitting unit surfaces arranged to lie on the surface of a cylinder the axis of which is coincident with a near end of a secondary prism, such as I I I, which is in the normal plane for propagation with the radiating units driven in phase. The principles involved are, of course, identical with those discussed in my copending application of January 6, 1942, mentioned above, with respect to focusing prismatic devices.

A compound (or doubly) prismatic system for electromagnetic waves employing the simple electromagnetic prisms of my copending application entitled Pipe Antennas and Prisms, Se rial-No. 381,236, filed March 1, 1941, now United States Patent 2,408,435, granted October 1, 1946, can readily be assembled in the light of the above disclosures which will be closely analogous to the compressional wave system of Fig. 5 described above.

Electromagnetic Wave object-location, navigational or communicating systems employing compound or doubly prismatic radiating devices are shown in Figs. 6, 7 and 8 and will now be described.

In Fig. 6 a spark-gap oscillator I20, of any of numerous types well known in the art, generates a broad band of ultra-high frequencies. The out put of oscillator I is passed through filter I22 which selects a band of frequencies appropriate for use in the system. The primary electromagnetic prism I24 can be, by way of example, a plurality of prisms of the type shown in Fig. 1 of my above-mentioned copending application Serial No. 381,236, now Patent 2,408,435, arranged adjacent to each other with their orifices all facing to the left. Prism I26, which may be of bees- 10 wax, serves to focus the energy emitted by prism I24 on a line perpendicular to the plane of the paper the vertical position of which is determined by the direction in which the energy is radiated by prism I24. Secondary prisms I28 to I32 each comprise, for example, a plurality of wave guide filters of the type illustrated in Fig. 18 of my above-mentioned application and consisting of a Wave guide with transverse members having orifices therein placed at regular intervals along the interior of the guide. In this instance, however, the holes in the side of the wave guide are omitted and the energy-absorbing termination is replaced by an electromagnetic horn radiator. Each of the secondary prisms I28 to I 32, inclusive, then consists of a plurality of such wave-guide filter and horn structures aligned perpendicular to the plane of the paper and analogous in structure and arrangement to the compressional wave system secondary prisms described above. The secondary prisms are, of course, proportioned to laterally spread a particular portion of the total electromagnetic wave frequency range of the system so that again we have a system in which vertical distribution of frequency groups is effected by a primary prismatic device and horizontal distribution of the frequencies of each group is effected by a secondary prismatic device and the over-all effect is to' cover an area, each unit of the area having directed to it a particular frequency within the range of the system.

For object-detection by the reflection method a receiving system, including loop antenna I40 which may be oriented to receive reflections from the area toward which energy is transmitted, a filter I 42 to exclude frequencies outside the range transmitted, an amplifier I44, a series of filters including filters I46, I40, I50 to isolate reflections of difierent frequency, a like series of rectifiers including rectifiers I52, I54 and I56 to rectify the energy of each isolated frequency and an indicating device I58 having indicating units including units I60, I62 and I64 to indicate the reflected frequencies which are received, can be employed. The location of the indicating units I60, etc., on the face of the indicating device I58 can, of course, correspond to the location of points in the area toward which the respective frequencies are transmitted, which, upon reception after reflection, cause the operation of the particular, respective, units so that a glance at the indicating device I50 will sufiice to show the number and relative positions in the area of a plurality of objects from which reflections are received.

The system of Fig. '7 may also be employed for object-location or similar purposes. In Fig. '7 a spark-gap oscillator 2 I8 generates a wide band of ultra-high frequencies, a filter 2I6 selects an appropriate range of frequencies from the band generated by oscillator 2I8, antenna 2 I4 radiates the frequencies selected by filter 2IB. Antenna 2 I 4 may be non-directive but is preferably broadly directive so that it may cover an appropriate area to be investigated. A compound (or doubly) prismatic device 220, similar to the combination of primary prism I24, lens I26 and secondary prisms I28 to I32, inclusive, of Fig. 6, by way of example, is employed in the system of Fig. 7 to receive reflections from a predetermined area of the energy emitted by antenna 2 I4. Filter 222 serves to exclude frequencies outside the range emitted by antenna 2 I4. Amplifier 224 amplifies the frequencies received and a second com- 1 1 eeps risma c dev e 2. am e s r t distribute the amplified received reflected frequencies' over'ari area covered by anfas'se'nrbiy of sr'n detecting units includ'ng units 2'40 to 24s; in we, which upon being struck by a received reflectedfrequency; energize particular indicating units of a group including un'ts' 250' to 258, inclusive. for the' System of Fig. 6, the indicating units may be arranged to show at a Withgame 'the' number and relativepositions,

in the areacovered by the receiving compound prism 2'26; ofobjects 'from which reflections are obtained. Since all frequencies of the range passed by filter 216 are broadcast by antenna 214 over the area covered by receiving prism 220', all reflections will include all frequencies of this range. The'prism- 220 however, will discriminate respect to angle of approach and will select a different frequency from each of a number of reflections approaching at different angles, the

particular frequency each case corresponding to the particular axi'gie' of approach.

Fig. 8 another form of system employing a compound or do'u'bly prismatic "device is shown. willpresently become apparent systems of this type can be employed for switching radio m'tra fmitt'e' by noting the ire uency o f'the signal received. If the two-way gOinmi-inicating feature, to be desc ibed presently, is employed the parties at both "station's ean determine the direction to he other static! by noting the frequen'ey at which they are operating.

"a voice-frequency radio beani switching st mirr 23 w -tar emmuni n a plurality of channels having particular known direetivities', with reier'enee to Fig. 8 113. is desired, r gentle 9 c g at s? m? b plurality of inciv ifi W se fis iiens q d e Ill, it, l83,toany one of a plurality of outcfin' 'i re enc w -mu li es 8L 1- a in min li e. iQr' exam le in onn t 'h 'su 'h. a Suitable te n se l including transformer H2 with a modulator H4 d qe qdula '15 sctsd in Pa all ii lil pu s indica in th d i ed New x e wh h subs flssr wishes t a miec a are i sei law Hi we il t 'iq' fr i sm .91 ha t e qqu le ass mma net fir smat em includ ng rim y rism ifi f .in 9 R38. ss 'esq ar Pri ms 0 9 @2 9 s anner musin lense W to I95, direct and focus the r'adig beam on the receiving antenna of the desired outgoing line, for example, antenna 210. Speech fromline l1| modulates the carrier generated in oscillator I18, receiving terminal set 284 includes a modulator; demodulator and transformer equivalent to and connected as are the modulator H4, demodulator I16 and transformer I12 of set H0. The carrier and speech side-bands generated in oscillator I18 are then transmitted to terminal set 234 which mo ula s the cs inbma iqn and s nds t speech currents out on line 283 as desired. When Any other combination of lines being used at the same time will also returnspeech tothe demodulator of line IH'butsinee the carriers-0t any other such lines will be of Qsubstantially'different frequency from that of osciilator" ITBQ, in-

terfering speech energy when demodulated will fall into a frequency range outside the voice frequency range and will not be heard by the party on line 11!, $everal or all, incoming lines can thus be connected't'o different outgoing hires and maintain conversations simultaneously without interfering with each other.

The system will function equally well if thein coming lines are operating at carrier telephone frequencies. In such 'a cas'e the controiiingbscillater is biased to take into account the setfrequency of the incoming carrier wave.

A central office haridlingltLOOO lines through one doubly prismatic device requires a degree of separation equivalent to alOO-Iine televisien cour e; fl i n represent a severe requirement. In Fig. {3 only three incomns. lines a d three ou oin li s and th P9?- i ns 9 he prisms s q'svis s r qqir t i rconnect them are indieated. remainderof the s em for a ver muc e en al lines u is 10,000, 1% a s??? anna would,

tem Th s 9? o nu se in l nl a du li a n Q the Pa s hown with 1 r fe s, na urall $9; as di n u sh n s's ncy lifr rs sss equ to d e a atipn 9? ach channe 1 52. a Qth r In t e. spec fic st u est qv i w e'c w th Fi 8 th radio. iin s @Q mr l t r la i l ver s o t, Obviously th b 911??" is a longer a ip nks were same principles could readily system in h h mu employed though m 9!} a s stem we wint r f links wg b bs imited'b mine aio s o a p ct a .a re to mu hlsss than 10,000- F ex m e a fixed lan sass la i be arranged to communicateselectively with a plurality of marine vessels and aircraft following designated lanes of travel. By calling in with hand of frequencies wide enough to include the frequency corresponding to its direction eaeh ra t an be oc e as to s rec i an subs?- quent communication can be carried through on the most appropriate frequency. By the use of focusing devices as suggested in B th e s tance of a particular or fft can be establishd and, thus its position can be definitely determined Alternatively with the master' station placed on the flagship a fleet of marine craft with Gooperating air patrol craft, can maintain a specified formation, each craft maintaining itself at the focal point for an energy beam of a particular predetermined frequency. For military uses such systems should employ the minimum power es sential for operation. The signals can of course be intermittent, if desired.

The above arrangements are illustrative of particular applications of theprinciplesl of the invention. Numerous other arrangement enibpdyii he Principles of t e i ve on u a ily be devised by those skilled in the art. The

the subscriber on line 283 talks, some of the ear;

13 scope of the invention is defined in the following claims.

What is claimed is:

1. In a compressional wave system fOI the de tection and location of noise emitting sources within a predetermined area, a compressionalwave prismatic receiving device adapted to directively receive from said area any frequency of a substantial band of frequencies within the frequency spectrum of the noise sources to be detected, each frequency within the said band being efficiently received'by said receiving device only if it approaches said receiving device from a pa ticular angle, frequency analyzing means for determining the frequencies received and means for indicating which frequencies within the said band are being received whereby the number and angular direction of noise sources within said area can readily be determined.

2. The compressional wave system of claim 1, the said means for determining the frequencies received comprising a modulator into which the received frequencies are introduced, a variable heterodyne oscillator, a band-pass filter passing substantially a single frequency, the frequency range of variation of said heterodyne oscillator including within it frequencies which when combined with any frequency within the band received by said prismatic receiving device will produce a beat-note frequency which will pass through the pass-band of said filter, the output of said heterodyne oscillator being introduced into said modulator, the output of said modulator being introduced into said filter, means for indicating the passage of energy through said filter and for simultaneously indicating the instantaneous frequenc of said heterodyne oscillator whereby the number and angular direction of noise sources within the area covered by said prismatic receiving device are readily determined.

3. The compressional wave system of claim 1, the means for indicating which frequencies are being received comprising a cathode ray indicator having a pair of horizontal deflecting plates and a control anode, the system including means for deflecting the beam of said cathode ray indicator horizontally in synchronism with the operation of the said frequency analyzing means, and means operatively interconnecting the said control anode and said frequency analyzing means for increasing the intensity of said cathode ray beam whenever said analyzing means obtains a positive indication of the presence of a received frequency whereby a line pattern of indications of points of increased intensity of said cathode ray is obtained, the number of said points corresponding with the number of noise somces and the lateral positions of said points indicating the angular direction of the respective noise sources with respect to the said prismatic receiving device.

4. In an object-detecting system, a prismatic radiator proportioned to prismatically radiate a particular spectrum of frequencies to cover a region in space, means for periodically energizing said radiator with the said particular spectrum of frequencies, means for receiving reflections of said radiated frequencies, and means for determining the frequencies of the received reflected components whereby indications of the number and respective directions of reflecting objects within the said region are obtained.

5. In an object-detecting system, a prismatic receiver proportioned to prismatically receive a particular spectrum of frequencies selectively from a predetermined region in space, means for radiating said spectrum of frequencies into said region and means for determining the frequencies of the respective reflected components of said spectrum radiated into said region which are received whereby indications of the number and respective directions of reflecting objects within the said region are obtained.

6. In an object-detecting system, the system of claim 4, said prismatic radiator and said receiving means both being rotatable about their respective longitudinal axes whereby a more extensive region may be investigated and the number and respective directions of reflecting objects within said more extensive region may be determined. Ii

7. In a marine object-detecting system, a pris matically directive compressional wave receiver mounted on a rotatable longitudinal shaft, the shaft in turn being mounted beneath a marine craft substantially in a plane including the keel of the craft, the receiver being proportioned to prismatically receive a particular spectrum of compressional wave frequencies from points within a predetermined first area and to effectively exclude compressional wave frequencies from points within a predetermined second area including the area about the propellers of the craft, for all positions of said rotatable shaft whereby an extensive region beneath and to the sides of said vessel may be explored by rotating said shaft without interference from propeller noise from the craft itself and without requiring the slowing down or stopping of the driving engines of the craft itself.

8. In a system for detecting the presence and following the movement of submerged powerdriven craft, a plurality of submerged prismatically directive compressional wave receivers and means for determining and observing the frequencies received by each receiver whereby the presence and movement of submerged powerdriven craft may be detected and followed, respectively.

9. In an object-detecting system, a compound prismatically directive radiator comprising a primary prismatic device and lens, distributing in one direction a total frequency spectrum in portions to each of a plurality of secondary prismatic devices, the said secondary prismatic devices distributing their respective portions of said total frequency spectrum in a second direction whereby a substantial two-dimensional distribution of the energy of said spectrum is obtained.

10. In an object-detecting system, the radiator of claim 9 and means for receiving reflections of the energy radiated by said radiator and determining the frequency of the received reflections to obtain indications of the number and direction of reflecting objects in the area into which the radiator projects energy.

11. In an object-locating system, a radiator for prismatically distributing energy comprising a particular frequency spectrum over a large threedimensional region, means for receiving reflections of said energy from reflecting objects within said region, means comprising a plurality of filters for separating received reflections on the basis of their respective frequencies, a plurality of signal devices connected to the output ends of said filters and arranged on an indicating panel in order corresponding to the relative positions from which the frequencies passed by their respective associated filters are received, each W I ll of sa d si nal d vices operating when a refl ted component passes threugh respective associated filter whereby a pattern of indications is formed on said panel by the operated signal devices which is representative of thenumber and directions of the reflecting objects within the said region.

12. In a system for detecting mobile noise emitting craft, a prismatically receptive means responsive to a particular diiierent frequency of the noise for each .01 a wide range of particular different directions, respectively, and means for indicating the frequency received.

13. In an object detecting system, a prismatic means for directively radiating energy of a broad band of frequencies each frequency of said range being radiated in a particular difierent direction, means for receiving reflections of said radiated energy and determining the particular frequencies of the received reflected energy whereby the direction of the reflecting objects may be ascertained.

14,. In a system for detecting the direction and distance of objects within a particular area, means for periodically radiating energy pulses comprising a broad band of frequencies, each frequency of said range being radiated in a particular different direction, means {or receiving refiections of said pulses, means for separating the receiving reflected pulses on the basis of frequency differences and means for timing the interval for each received reflected frequency between emission of the pulse and receipt of the particular reflection whereby the received frequencies indicate the respective distances .of objects from which reflections are received.

WARREN P. MASON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,l86,735 Fessenden Mar. 11, 1924; 1,564,303 Wold Dec. 8, 1925 2,017,695 Hahnemann Oct. 15, 1935 2,169,304 Tournier Aug. 15, 1939 2,227,598 Lyman et a1. Jan. .7, 1941 2,232,858 Lane Feb. 25, 19 11 FOREIGN PATENTS Number Country Date 291,124 Germany Aug. 1, 1919 297,996 Germany Aug. 27, 1919 570,526 Germany Feb. 16, 1933 

